The tool selection of accessories is one of the important contents in CNC technology, which does not affect the efficiency of CNC machine tools, but also directly affects the quality of accessories. As the spindle speed and range of CNC machine tools are far higher than those of ordinary machine tools and automobile parts manufacturers, and the output power of the spindle is large, higher requirements are put forward for CNC tools compared with traditional methods, including high precision, high strength, good rigidity, high durability, stable size, convenient installation and adjustment. The characteristics of the spindle drive system of CNC machine tools are introduced. This requires the reasonable structure of the tool, the standardization and serialization of geometric parameters. Numerical control tool is one of the preconditions to improve efficiency. Its selection depends on the geometry of the workpiece, the material state, the rigidity of the fixture and the tool selected by the machine tool. The following aspects shall be considered:
(1) Select tools according to the cutting performance of accessory materials. For turning or milling steel, titanium alloy and stainless steel parts, it is recommended to use indexable carbide tools with good selectivity. (
2) Select the tool according to the hardware part stage. That is to say, the rough stage is mainly to remove the allowance, and the tools with good rigidity and low accuracy should be selected. The semi precision and fine stage are mainly to improve the accuracy and product quality of the parts, and the tools with high durability and high accuracy should be selected. The accuracy Z of the tools used in the rough stage is low, while the accuracy Z of the tools used in the fine stage is high. If the same tool is selected for coarse and fine selection, it is recommended to select the tool eliminated by fine selection for coarse selection, because the wear of the tool eliminated by fine selection is mostly slight wear of the edge, and the coating is worn and polished. The continuous use will affect the quality of fine, but the impact on coarse is small.
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(3) Select cutting tools and geometric parameters according to the characteristics of CNC lathe area. Tools with large diameter and small ratio of length to diameter shall be selected if the part structure allows; The end edge of the over center milling cutter for cutting thin-wall and ultra-thin wall parts shall have enough centripetal angle to reduce the cutting force of the cutter and the cutting part. For aluminum, copper and other soft material parts, end mills with slightly larger rake angle shall be selected, and the number of teeth shall not exceed 4. When selecting the tool, the size of the tool shall be compatible with the surface size of the workpiece.
In production, end mills are often used for the peripheral contour of planar parts; When milling the plane, the carbide insert milling cutter shall be selected; High speed steel end mills shall be selected for bosses and grooves; For rough surface or rough hole of hardware accessories, corn milling cutter with cemented carbide blade can be selected; Ball end milling cutter, ring milling cutter, cone milling cutter and disc milling cutter are often used for some solid surfaces and variable angle profiles. When carrying out free-form surface, because the end cutting speed of the ball end cutter is zero, the cutting line spacing is generally small for numerical control accuracy, so the ball end milling cutter is suitable for surface finishing. However, the end milling cutter is far from the ball end milling cutter in terms of surface quality and efficiency. Therefore, on the premise of ensuring that the parts are not cut, the end milling cutter shall be selected as much as possible for rough and semi fine surfaces. In addition, the relationship between the durability and accuracy of the tool and the price of the tool should be noted that in most cases, the selection of a good tool increases the cost of the tool, but the resulting improvement in quality and efficiency can greatly reduce the overall cost. On the center, the tool is pre installed in the tool library, and the corresponding tool change action is carried out through the tool selection and tool change instructions of the NC program. The corresponding standard tool holder suitable for the specification of the tool system of the machine tool must be selected so that the NC tool can be quickly and accurately installed on the spindle of the machine tool or returned to the tool magazine. The programmer shall be able to understand the structural dimension, adjustment method and adjustment range of the tool shank used by the machine tool, so as to determine the radial and axial dimensions of the tool and reasonably arrange the arrangement sequence of the tool during programming.